Tense, twisted spy novels — from John le Carré to Ian Fleming, Tom Clancy to Robert Ludlum — never seem to lose their audience appeal for film adaptations. That august group is now joined by the late Vince Flynn, the St. Paul author whose bestsellers about anti-terrorist lone wolf Mitch Rapp make their first appearance onscreen with “American Assassin.” It’s an origin story set up for a potential series, and it seems likely to make Rapp a recognizable character among moviegoers as well as page-turners.

Direct and economically structured, the film introduces us to Rapp (Dylan O’Brien, star of “The Maze Runner” franchise and TV’s “Teen Wolf”) during the best moments of his life. He and his lovely girlfriend move up to the fiancé level as he hands her an engagement ring in the gentle sea waves at a Caribbean resort.

Alas, as with James Bond and Jason Bourne, beauties who get close to Rapp are rarely brought back in long-running roles. A squad of ISIS-style terrorists hits the harbor, leaving scores of tourists dead and Rapp badly wounded.

Cut ahead 18 months and meet the new Mitch Rapp, transformed from charming romantic to stone-cold revenge engine. He has turned himself into an MMA fighter so savage that he’s banished from his gym. He has memorized the smallest details of the Qur’an and Hadith and mastered conversational Arabic to help him win the trust of the attack’s leader through internet contact. And he has become so skilled with bullets and blades that a Navy SEAL would groan with envy.

This cut-to-the chase opening moves fast, but like the film overall, it has a decent level of self-awareness. Rapp’s gunshot wounds have healed, but the film makes a nuanced case that wounds like that keep opening. Followed by CIA surveillance and recruited by the agency as a black ops agent, Rapp uses the position as a means to his personal end. But the same can be said for most of the members of Rapp’s ever-growing enemies list, from jihadist and political terrorists, Iranian interests and Ghost (Taylor Kitsch), a mercenary who wants to give the world a nuclear surprise package. Even Rapp’s hard-as-nails CIA instructor, Stan Hurley (Michael Keaton), has his own dog in the fight.

And fighting is what this film is about, with the special sauce of acting added as needed. This is good for the audience and for the star. O’Brien, moving from young adult territory, where films seem to be populated by models rather than actors, capably steps into his first mature role. He holds his own in one-on-one combat with the imposingly fit-looking Keaton as his CIA trainer, taking the pain so we can feel it. Sharing the screen with the actor who gave us “Beetlejuice,” “Batman,” “Birdman” and more is an equally daunting challenge, but he’s up to it.

The plot is typical potboiler fare, bounding from the United States to Lebanon to Italy as Rapp finds opportunities to retaliate ruthlessly for his loss. Supervising his first mission is Hurley, who essentially shouts: “You kill the people I tell you to kill when I tell you to kill them!”

How do you keep the tension always at the peak while piggybacking nearly nonstop close-quarters fighting? By changing the details, terminating this villain with a knifelike shard of broken glass, dropping another character with a long-distance rifle or a fast-moving car, waterboarding another in a filled bathtub, then making the next battle one between Rapp and three inflamed guard dogs.

Less thrilling are the driving stunts, with cars zipping around the streets of Rome in ways that are reasonably fast but hardly furious. I have seen better chase scenes in Honda commercials.

That said, the final sequence, putting a thermonuclear device at sea, is the kind of crash-smash doozy you would see in a Transformers movie, with a Navy aircraft carrier and several battleships being tossed here and there like carp jumping out of the water. Director Michael Cuesta (a TV veteran from “Dexter” and “Six Feet Under”) uses the main body of the film as a long fuse and delivers a mind-numbing boomfest at the climax. The film is an entertaining introduction to Rapp, whose final scene implies that he has a lot more retaliation to inflict. He could become a brand-name mainstay of the American superspy market for decades to come.